**Number System Questions for RRB Group-D Set-2 PDF**

Download Top-14 RRB Group-D Number System Questions set-2 PDF. RRB GROUP-D Maths questions based on asked questions in previous exam papers very important for the Railway Group-D exam.

Download Number System Questions for RRB Group-D Set-2 PDF

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**Question 1: **What is the Lowest Common Factor of 81, 108 and 210?

a) 1

b) 3

c) 7

d) 9

**Question 2: **What is the HCF of 90, 135, 210?

a) 3

b) 6

c) 9

d) 15

**Question 3: **x and y are the smallest two digit prime numbers such that x = 2y + 1. What is the value of x – y?

a) 12

b) 18

c) 24

d) 30

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**Question 4: **What is the LCM of $7^5*8^6$, $7^3*8^4*9^2$ and $7^4*8^5*9$?

a) $7^3*8^4$

b) $7^3*8^4*9^3$

c) $7^5*8^6*9^2$

d) $7^6*8^7*9^3$

**Question 5: **What is HCF of 195, 390, 312 and 702?

a) 7

b) 13

c) 39

d) 65

**Question 6: **Which is the smallest number which when divided by 5,6 and 7 leaves a remainder of 2?

a) 212

b) 262

c) 282

d) 302

**Question 7: **Which of the following is NOT a prime number?

a) 43

b) 53

c) 71

d) 91

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**Question 8: **If the square root of 5.44802281 is 2.3341, what is the square root of 5448022.81?

a) 23341.1

b) 2334.1

c) 233.41

d) 23.341

**Question 9: **What is the HCF of 28, 42 and 56?

a) 0

b) 1

c) 7

d) None of the above

**Question 10: **What is the LCM of $3^2 * 2^3$, $4^2 * 3 * 2$ and $3^3 * 2 ^4$?

a) 864

b) 5184

c) 7776

d) 3888

**Question 11: **What is the Highest common factor of: 391, 483, 943 and 253?

a) 17

b) 19

c) 21

d) 23

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**Question 12: **What is the range of the following numbers?

19, 23, 17, 25, 18, 20, 20, 31, 16

a) 15

b) 18

c) 20

d) 22

**Question 13: **If 9765X is divisible by 11, what is the value of X?

a) 1

b) 3

c) 4

d) 8

**Question 14: **Which of the following numbers is NOT a multiple of 225?

2025, 2925, 5675, 6975

a) 2025

b) 2925

c) 5675

d) 6975

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**Answers & Solutions:**

**1) Answer (A)**

The lowest common factor of any set of natural numbers is 1. The Highest Common Factor of these three numbers is 3.

**2) Answer (D)**

90 = 3 * 3 * 2 * 5

135 = 5 * 3 * 3 * 3

210 = 2 * 5 * 3 * 7

So, 3 * 5 is the common factor of the three numbers.

**3) Answer (A)**

Since we are interested in the smallest two digit prime numbers, let’s start with the number 11.

If y = 11, x = 2 * 11 + 1 = 23, which is also a prime number.

So, the (x,y) set (23,11) satisfies the condition of 1) Prime numbers 2) Two digits 3) x = 2y + 1. So, the required answer is x – y = 23 – 11 = 12

**4) Answer (C)**

The numbers are $7^5*8^6$, $7^3*8^4*9^2$ and $7^4*8^5*9$.

Since, 7, 8, 9 are relatively prime, LCM of the given three numbers will contain the highest powers of 7,8,9 from all the given numbers.

Highest power of 7 is 5

Highest power of 8 is 6

Highest power of 9 is 2

So, LCM =$7^5*8^6*9^2$

**5) Answer (C)**

195 = 39 * 5

390 = 39 * 10

312 = 39 * 8

702 = 39 * 18

So, the HCF is 39

**6) Answer (A)**

The number is the LCM of 5,6 and 7 plus 2

So, 5 * 6 * 7 = 210 + 2 = 212

**7) Answer (D)**

91 = 7 * 13

**8) Answer (B)**

5448022.81 = 5.44802281 * $10^6$

So, $\sqrt{5.44802281 * 10^6}$ = 2.3341 * 1000 = 2334.1

**9) Answer (D)**

14 * 2 = 28

14 * 3 = 42

14 * 4 = 56

So, the Highest Common Factor of 28, 42 and 56 is 14.

**10) Answer (A)**

The numbers can be arranged as 3 * 24, 4 * 24, 18 * 24

So, 24 is common in all the three numbers.

So, the LCM = LCM( 3 , 4 ,18 ) * 24 = 36 * 24 = 864

**11) Answer (D)**

23 * 11 = 253

23 * 17 = 391

23 * 21 = 483

23 * 41 = 943

So, the HCF of the given numbers is 23

**12) Answer (A)**

The range of the numbers is given by the largest number – the smallest number = 31 – 16 = 15

**13) Answer (D)**

The divisibility test is that the sum of alternating numbers is divisible by 11.

So, 9 + 6 + x – 7 – 5 is divisible by 11

So, x has to be 8.

**14) Answer (C)**

225 * 9 = 2025

225 * 13 = 2925

225 * 31 = 6975

Only 5675 is not a multiple of 225

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